• Women's Health Nursing
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• v.15 no.2
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• pp.108-120
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• 2009

Purpose: This study aimed to explore the subjective sleep quality of depressed and non-depressed mothers in the late postpartum period and to determine the relationship with their health promoting behaviors, family functioning, parenting stress. Method: A non-probability sample of 128 mothers completed a self-administered questionnaires at 4-6weeks postpartum. The Edinburgh postnatal Depression Scale (EPDS) and Pittsburgh Sleep Quality Index were used to measure mother's experiences of depression symptoms and sleep. Related factors of sleep quality were measured by the Korean Family Functioning Scale, Health Promoting Lifestyle Profile, and Parenting Stress Index. The data was analysed using t-test, one-way ANOVA, and the Pearson's correlation coefficients. Result: The results indicated that the depressed mothers (EPDS$\geq$ 10) had poorer sleep quality than the non-depressed mothers(EPDS < 10), reported shortened sleep duration, and experienced more daytime dysfunctions. Depressed mothers who had no job, did not drink coffee, and were primipara tended to report poorer sleep quality. There were significant correlation between poorer sleep quality and lower health promoting behaviors, higher family intimacy and lower family communication, and higher parenting stress among depressed mothers. Conclusion: Our findings support the view that depressed mothers' experiences of poor sleep are much higher than non-depressed mothers and multi-faced. Nurse professionals should screen for sleep problems in the depressed mothers with a different biopsychosocial and behavioral aspect from the non-depressed mothers in the late postpartum period.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.31-41
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• 2019

Structural integrity assessment of piping components is of paramount important for remaining life prediction, residual strength evaluation and for in-service inspection planning. For accurate prediction of these, a reliable fracture parameter is essential. One of the fracture parameters is stress intensity factor (SIF), which is generally preferred for high strength materials, can be evaluated by using linear elastic fracture mechanics principles. To employ available analytical and numerical procedures for fracture analysis of piping components, it takes considerable amount of time and effort. In view of this, an alternative approach to analytical and finite element analysis, a model based on relevance vector machine (RVM) is developed to predict SIF of part through crack of a piping component under fatigue loading. RVM is based on probabilistic approach and regression and it is established based on Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Model for SIF prediction is developed by using MATLAB software wherein 70% of the data has been used for the development of RVM model and rest of the data is used for validation. The predicted SIF is found to be in good agreement with the corresponding analytical solution, and can be used for damage tolerant analysis of structural components.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.265-272
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• 2023

The aim of this study was to develop a new in-situ observation method and instrument in micro-scale to investigate the mechanism of stress corrosion cracking (SCC) initiation of Ni-base alloys in a high temperature water environment of pressurized water reactors (PWRs). A laser confocal microscope (LCM), an autoclave with diamond window view port, and a slow strain-rate tester with primary water circulation loop system were components of the instrument. Diamond window, one of the core components of the instrument, was selected based on its optical, chemical, and mechanical properties. LCM was used to observe the specimen in micro-scale, considering the experimental condition of a high-temperature primary water environment. Using in-situ method and instrument, it is possible to observe oxidation and deformation of specimen surface in micro-scale through the diamond window in a high-temperature primary water in real-time. The in-situ method and instrument developed in this work can be utilized to investigate effects of various factors on SCC initiation in a high-temperature water environment.

• Computers and Concrete
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• v.31 no.6
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• pp.469-484
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• 2023

The response mechanism of simply supported two-way reinforced concrete (RC) slabs under fire was numerically studied from the view of stress redistribution using the finite element software ABAQUS. Results show that: (1) Simply supported two-way RC slabs undergo intense stress redistribution, and their responses show four stages, namely elastic, elastic-plastic, plastic and tensile membrane stages. There is no cracking in the fire area of the slabs until the tensile membrane stage. (2) The inverted arch effect and tensile membrane effect improve the fire resistance of the two-way slabs. When the deflection is L/20, the slab is in an inverted arch effect state, and the slab still has a good deflection reserve. The deformation rate of the slab in the tensile membrane stage is smaller than that in the elastic-plastic and plastic stages. (3) Fire resistance of square slabs is better than that of rectangular slabs. Besides, increasing the reinforcement ratio or slab thickness improves the fire resistance of the slabs. However, an increase of cover thickness has little effect on the fire resistance of two-way slabs. (4) Compared with one-way slabs, the time for two-way slabs to enter the plastic and tensile cracking stage is postponed, and the deformation rate in the plastic and tensile cracking stage is also slowed down. (5) The simply supported two-way RC slabs can satisfy with the requirements of a class I fire resistance rating of 90 min without additional fire protection.

• Earthquakes and Structures
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• v.23 no.4
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• pp.363-371
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• 2022

Traditional metal dampers have disadvantages such as a higher yield point and inadequate adjustability. The experimental results show that the low yield point steel has superior energy dissipation hysteretic capacity and can be applied to seismic structures. To overcome these deficiencies, a novel compound metal damper comprising both low yield point steel plates and common steel plates is presented. The optimization objectives, including "maximum rigidity" and "full stress state", are proposed to obtain the optimal edge shape of a compound metal damper. The numerical results show that the optimized composite metal damper has the advantages such as full hysteresis curve, uniform stress distribution, more sufficient energy consumption, and it can adjust the yield strength of the damper according to the engineering requirements. In view of the mechanical characteristics of the compound metal damper, the equivalent model of eccentric cross bracing is established, and the approximate analytical solution of the yield strength and the yield displacement is proposed. A nonlinear simulation analysis is carried out for the overall aseismic capacity of three-layer-frame structures with a compound metal damper. It is verified that a compound metal damper has better energy dissipation capacity and superior seismic performance, especially for a damper with double-objective optimized shape.

• Steel and Composite Structures
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• v.50 no.4
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• pp.403-418
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• 2024

In this paper, vibration and energy absorption characteristics of a nanostructure which is composed of two embedded porous annular/circular nanoplates coupled by a viscoelastic substrate are investigated. The modified couple stress theory (MCST) and the Gurtin-Murdoch theory are applied to take into account the size and the surface effects, respectively. Furthermore, the structural damping effect is probed by the Kelvin-Voigt model and the mathematical model of the problem is developed by a new hyperbolic higher order shear deformation theory. The differential quadrature method (DQM) is employed to obtain the out-of-phase and in-phase frequencies of the structure in order to predict the dynamic response of it. The acquired results reveal that the vibration and energy absorption of the system depends on some factors such as porosity, surface stress effects, material length scale parameter, damping and spring constants of the viscoelastic foundation as well as geometrical parameters of annular/circular nanoplates. A bird's-eye view of the findings in the research paper offers a comprehensive understanding of the vibrational behavior and energy absorption capabilities of annular/circular porous nanoplates. The multidisciplinary approach and the inclusion of porosity make this study valuable for the development of innovative materials and applications in the field of nanoscience and engineering.

• Industry Promotion Research
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• v.9 no.1
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• pp.123-132
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• 2024

The purpose of this study was to improve the understanding of stress coping in the very old and elderly and to improve life satisfaction through stress reduction as the population ages. To this end, this study aimed to test the mediating effect of social support on the relationship between stress coping and life satisfaction among very old people. In particular, we paid attention to the differences in stress coping from the existing elderly population and took the view that they should be studied as an independent group. To confirm this, we analysed 275 men and women aged 85 years and older who responded to the fifth supplementary survey of the National Elderly Security Panel (KReIS) conducted by the National Pension Service. IBM SPSS 26 was used to test the mediating effect of social support on the effect of stress coping measures on life satisfaction in the very old elderly. The results of the significance test of the independent variables on the mediating variable showed that stress coping was positively significant, i.e., the higher the level of stress coping, the higher the life satisfaction. In addition, the results of the significance test of the effects of the independent variables and mediators on the dependent variable showed that coping with stress had a significant effect, and the mediator, social support, also had a significant effect on life satisfaction. Therefore, this study suggests the need for social support to improve the level of life satisfaction through coping with stress in the very old elderly.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.699-705
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• 2011

High-maneuver missile is a projectile which demands a strong momentum at short time. To produce a necessary thrust for the flight, the gas of high temperature and pressure is generated through explosive combustion of solid propellant, and a great thrust can be obtained by expanding this high temperature and pressure gas. Although the operating time of a rocket motor is less than a few seconds, a failure of part or ablation near the throat of nozzle may take place during the expansion of high temperature and pressure gas for great thrust. In other words, for the precise control of a missile an exact stress analysis considering both, the thermal stress caused by the heat transfer between combustion gas and wall, and the mechanical stress caused by the pressure change in the flow, should be considered first. In this connection, this study investigated the safety, as a point of view of stress and melting point of the material, of the pre-designed thrust generating structure which is subjected to high temperature and pressure as a function of motor operating time.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.21
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• pp.9467-9470
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• 2014

Background: Research indicates that oxidative stress induced by smoking plays a role in breast cancer. In view of these reports, we aimed to study th relationship between smoking and oxidative stress in breast cancer patients from the western region of Nepal. Materials and Methods: The study included a control group of 42 females (non-smoking healthy women) and a test group sudivided into Group I consisting of 46 female breast cancer patients who were smokers and Group II consisting of 42 non-smoking breast cancer patients. Detailed history of the patients was collected with the help of pre-test proforma. Plasma levels of malondialdehyde (MDA), total antioxidant activity (TAA) which represents total dietary antioxidants, vitamin C and ${\alpha}$- tocopherol were estimated by standard methods. Statistical analysis was done using SPSS version 16. Results: The plasma MDA, TAA, vitamin C and ${\alpha}$- tocopherol were $1{\pm}1.4nmol/ml$, $918{\pm}207{\mu}mol/L$, $1{\pm}0.24mg/dL$ and $0.94{\pm}0.31mg/dL$ in controls, $5{\pm}1.2nmol/ml$, $458{\pm}166{\mu}mol/L$, $0.64{\pm}0.32mg/dL$ and $0.5{\pm}0.3mg/dL$ in Group-I and $2.56{\pm}1.2nmol/ml$, $663{\pm}178{\mu}mol/L$, $0.78{\pm}0.2mg/dL$ and $0.77{\pm}0.2mg/dL$ in Group- II, respectively. Vitamin C, ${\alpha}$- tocopherol and TAA (p=0.001) were significantly reduced whereas MDA (p=0.001) was significantly raised in Group-I when compared to controls and Group-II. Conclusions: We observed a significant rise in oxidative stress and low levels of antioxidants in breast cancer patients with smoking habit. It is well known that free radicals facilitate the progression of breast cancer, possibly increasing the risk of progression to the next stage.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.629-639
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• 2002

In-vitro flow characteristics downstream of a polyurethane artificial heart valve and a Bjork-Shiley Monostrut mechanical valve have been comparatively investigated in pulsatile flow using particle image velocimetry (PIV). With a triggering system and a time-delayed circuit the velocity distributions on the two perpendicular measurement planes downstream of the valves are evaluated at any given instant in conjunction with the opening behaviors of valve leaflets during a cardiac cycle. The regions of stasis and high shear stress can be found simultaneously by examining the entire view of the instantaneous velocity and Reynolds shear stress fields. It is known that high shear stress regions exist at the interface between strong axial jet flows along the wall and vortical flows in the central area distal to the valves. In addition. there are large stagnation or recirculation regions in the vicinity of the valve leaflet, where thrombus formation can be induced by accumulation of blood elements damaged in the high shear stress zones. A correlation between the unsteady flow patterns downstream of the valve and the corresponding opening postures of the polyurethane valve membrane gives useful data necessary for improved design of the frame structure and leaflet geometry of the polyurethane valve.